The present invention relates to a cement mixture blowing device capable of blowing not only a dry cement mixture but also a highly viscous cement mixture mixed with water.
The methods and devices for blowing a cement mixture (which refers to "a cement mortar mixture, a concrete mixture and so on" in this specification) have long been investigated, and various cement guns have been devised and demonstrated. However these prior art cement mixture blowing devices have been solely designed to blow a dry mixture of cement and sand. That is, the mixture of cement and sand in suitable ratio is blown through a nozzle by the air jet, and water is added to the mixture in the nozzle to give cohesion at the point of impact.
When cement and water is proportioned in suitable ratio, mixed well, placed and cured, a uniform and high quality structure and adequate durability may be obtained. However, with the prior art cement gun, the mixture of cement and sand cannot be well mixed and kneaded with water so that the mixture is blown before water is sufficiently diffused among the cement particles. As a result, finely divided water and cement particles are alternately impinged against an object surface so that a segregation of cement particles and the nonuniform structure tends to occur very frequently. In addition, an operator must check the cohesion of the impinged cement mixture so as to control the volume of water added to the cement-sand mixture by operating control means attached to the nozzle. As a consequence, insufficient supply of water frequently results. Furthermore, with the prior art cement mixture blowing devices, the experience and skill of the operator greatly influence the quality of cement mixture placed. For instance, an unskilled operator tends to blow the cement mixture in the form of a layer so that the non-uniform structure and insufficient strength or durability result.
In order to solve these problems, there has been invented and demonstrated a cement mixture blowing device of the type disclosed in, for instance, U.S. Pat. No. 3,161,442. In this device a cement mixture is fed into pockets of a rotary disk so that upon rotation of the rotary disk, the pockets filled with the cement mixture are successively brought to a discharge or unloading station. In the discharge station the pocket is hermetically sealed, and the air under pressure is admitted into the sealed pocket so that the cement mixture is discharged through a discharge pipe and blown through a nozzle against an object surface. When the cement mixture is completely or almost dried, its viscosity is low so that the cement mixture may be smoothly fed into the pockets of the rotary disk, discharged through the discharge pipe and blown through the nozzle in a satisfactory manner. However, when water is proportioned, mixed and kneaded with the cement mixture, the viscosity of the cement mixture increases so that the cement mixture tends to bridge over the pockets of the rotary disk and will not drop into them. As a result, empty pockets are successively transported to the discharge or unloading station so that no cement mixture can be blown. If the agitator blades are so arranged as to break such bridge, this problem may be solved. However, in practice such arrangement is impossible because of the installation space of the blow and discharge pipes. That is, the agitator blades cannot pass in close proximity to the top surface of the rotary disk. Thus, the cement mixture blowing device disclosed in U.S. Pat. No. 3,161,442 cannot blow a highly viscous cement mixture mixed with water.